Entomopathogenic role of a non-core Pseudomonas protegens strain associated with Steinernema feltiae. International Congress on Invertebrate Pathology and Microbial control

While the bioinsecticidal action of entomopathogenic nematodes (EPNs) typically relies on their symbiosis with core bacteria, other non-core species could be involved in pathogenesis. The role of a novel Pseudomonas protegens strain isolated as the main agent of septicaemia in larvae of the wax moth, Galleria mellonella, infected with a soil dwelling Steinernema feltiae strain was investigated. The association of P. protegens with nematodes appeared to be robust and the bacterium appeared to be well-adapted to the insect haemocoel, being able to rapidly proliferate after the injection of an even small amount of living cells (100 CFU) to a larva, causing its fast death. The bacterium was also able to act by ingestion against G. mellonella larvae (LC 50 = 4.0 × 10 CFU/ml), even if with a slower action. Specific bioassays showed varying levels of bacterial virulence on diverse target Diptera and Lepidoptera. P. protegens appears to have evolved its own potential as a stand-alone entomopathogen, however, the establishment of a stable association with entomoparasitic nematodes, would represent a special competitive advantage.